Chemistry Paper 3A WASSCE (SC), 2020

Question 2A

 

C is an organic compound. Carry out the following exercises on C.
Record your observations and identify any gas(es) evolved. State the conclusion you draw from the results of each test.

  1. Put about 10 drops of C on a watch glass and ignite it using a burning splint.
  2. (i)         Put about 1 cm3 of C in a test tube and add about 1 cm3 of distilled water. Shake the test 
  3.              tube.
    (ii)        Put about 1 cm3 of C in a test tube and add about 2 cm3 of acidified K2Cr2O7 solution. Warm the mixture gently and leave to stand for 5 minutes.

  4. Put few crystals of specimen D in a test tube and add about 2 cm3 of C followed by about 2 cm3 of 10% NaOH(aq). Shake the test tube vigorously.
  5. State the class of compounds to which C belongs.

Observation

 

This question tested skills on qualitative analysis with sequence of instructions. The performance of candidates was average in this question.

In part (a), few candidates wrote correct observations.

In part (b), majority of the candidates could not deduce correct inferences from their observations.

In part (c), majority of the candidates did not provide sufficient information about their observations. So they lost some marks to inadequate observations.

In part (d), majority of the candidates could not state the class of compounds to which C belongs.

The expected answers include: